This invention relates to a means for generating heat by way of an electrochemical reaction, and, more specifically, to a means for sustaining an electrochemical reaction in a heating element at high rates for extended periods of time.
The prior art as taught by Kober (U.S. Pat. No. 3,774,589) describes an electrochemical heater construction having an anode structure and cathode structure and a suitable porous, highly absorbent separator means situated therebetween, the electrode structures being connected one to another internally by electrically conductive short circuiting members. Introduction of a suitable electrolyte into this construction initiates an electrochemical heat-producing reaction.
It has been shown on theoretical grounds that this heater construction results in efficiencies of energy conversion, (that is, the conversion of the chemical energy inherent in the electrochemically active materials to thermal energy) approaching 100%. However, in practice, although the energy conversion reaction proceeds at an efficiency approaching 100%, utilization of the electrochemically active materials is well below this value. Only a small percentage of the active material available for reaction is actually utilized. Stated differently, the construction taught by Kober in U.S. Pat. No. 3,774,589 is not capable of sustaining the electrochemical reaction at high rates until the active materials have been completely exhausted. An important practical limitation resulting from the limited electrochemical reaction is that excess active materials must be part of the heater construction, thus adding considerably to the size and cost of the heater for practical applications.
The electrochemical heater design of this invention, which places two cathode structures about a single anode, not only permits the high rate (high current with minimal polarization) generation of heat, but also allows the electrochemical reaction to sustain itself substantially until the exhaustion of the active material, within the limits of practicality.